Discussion welcome/wanted on discussion tab.

Mozilla Firefox Pros(I have version 3.0)

you can add cool add-ons such as password managers, Smart bookmark toolbars, StumbleUpon, etc.(any version)
you can select themes to change the appearance of your browser(any version)
it is faster than quite a few other web browsers(almost all versions)
built-in spell-checker(some versions)
smart in the computer sense(all versions)
fast(almost all versions)
good details(most versions)
easy to use(all versions)
Much, much more!